#include<iostream>
#include<vector>
#include<queue>
#include<cstring>
#include<cmath>
#include<map>
#include<set>
#include<cstdio>
#include<algorithm>
#define debug(a) cout<<#a<<"="<<a<<endl;
using namespace std;
const int maxn =1000000+5;
typedef long long LL;
const int mod=1e9+7;
inline LL read(){LL x=0,f=1;char ch=getchar();	while (!isdigit(ch)){if (ch=='-') f=-1;ch=getchar();}while (isdigit(ch)){x=x*10+ch-48;ch=getchar();}
return x*f;}
LL qp(LL a,LL b,LL mod){LL ans=1;if(b==0){return ans%mod;}while(b){if(b%2==1){b--;ans=ans*a%mod;}a=a*a%mod;b=b/2;}return ans%mod;}
LL ksm(LL a,LL k) {
    LL res = 1;
    while(k>1) {
        if(k&1) res = (res * a) % mod;
        k >>= 1;
        a = (a * a) % mod;
    }
    return res%mod;
}
LL a[110]={1,682498929,491101308,76479948,723816384,67347853,27368307,625544428,199888908,888050723,927880474,281863274,661224977,623534362,970055531,261384175,195888993,66404266,547665832,109838563,933245637,724691727,368925948,268838846,136026497,112390913,135498044,217544623,
419363534,500780548,668123525,128487469,30977140,522049725,309058615,386027524,189239124,148528617,940567523,917084264,429277690,996164327,358655417,568392357,780072518,462639908,275105629,909210595,99199382,
703397904,733333339,97830135,608823837,256141983,141827977,696628828,637939935,811575797,848924691,131772368,724464507,272814771,326159309,
456152084,903466878,92255682,769795511,373745190,606241871,825871994,957939114,435887178,852304035,663307737,375297772,217598709,624148346,671734977,624500515,748510389,203191898,423951674,629786193,672850561,814362881,823845496,116667533,256473217,627655552,245795606,586445753,172114298,193781724,778983779,83868974,315103615,965785236,492741665,377329025,847549272,698611116};
LL pre1(LL n,LL r,LL c,LL w){
    LL res=a[n];
    for(LL i=n*10000000+1;i<=r;i++){
        res=res*i%mod;
    }
    return res;
}
LL pre2(LL n,LL r,LL c,LL w){
    LL res=a[n];
    for(LL i=n*10000000+1;i<=c;i++){
        res=res*i%mod;
    }
    return res;
}
LL pre3(LL n,LL r,LL c,LL w){
    LL res=a[n];
    for(LL i=n*10000000+1;i<=w;i++){
        res=res*i%mod;
    }
    return res;
}
void solve(LL n,LL k){
    LL p=mod;
    k=n-k;n++;
    LL r=n-2;LL c=k-1;LL w=r-c;
    LL no=r/10000000;
    LL ans1=pre1(no,r,c,w);
    no=c/10000000;
    LL ans2=pre2(no,r,c,w);

    no=w/10000000;
    LL ans3=pre3(no,r,c,w);

    printf("%lld\n",ans1%mod*qp(ans2*ans3%mod,mod-2,mod)%mod*qp(n-1,n-k-1,mod)%mod);
}
int main(void)
{
    LL n,k;
    n=read();k=read();
    solve(n,k);
return 0;
}
